Synthesis and Crystallization Behavior of Equisequential ADMET Polyethylene Containing Arylene Ether Defects: Remarkable Effects of Substitution Position and Arylene Size

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• 作者：Shao-Fei Song ; Yin-Tian Guo ; Rui-Yang Wang ; Zhi-Sheng Fu ; Jun-Ting Xu ; Zhi-Qiang Fan
• 刊名：Macromolecules
• 出版年：2016
• 出版时间：August 23, 2016
• 年：2016
• 卷：49
• 期：16
• 页码：6001-6011
• 全文大小：578K
• 年卷期：0
• ISSN：1520-5835

文摘

A new series of polyethylene (PE) containing arylene ether units as defects in the main chain, which were precisely separated by 20 CH₂ units, were synthesized via acyclic diene metathesis (ADMET) polymerization. The thermal stability, crystallization, and melting behaviors, crystal structure, and chain stacking were investigated with TGA, DSC, WAXD, and SAXS. It is found that the substitution position in the arylene units has a remarkable influence on the chain stacking and their location in the solid phase. The ortho-substituted phenylene units are excluded from the crystal phase, leading to a low melting temperature (T_m). In contrast, the para-substituted phenylene units can be included into the crystal, leading to a high T_m. The meta-substituted phenylene units can be partially included into the crystal, resulting in mixed crystal structures and an intermediate T_m. Such an effect of substitution position in precision PEs is different from that in poly(ethylene oxide) reported in the literature, which can be ascribed to the matchable configuration of the defects in the main chain with the conformation of PE in the crystals. When the defects become naphthylene ether units, the crystallization and melting behaviors of the polymers are similar to or different from those of the precision PEs with phenylene ether defects, depending on the substitution position. This shows that both the substitution position in the arylene ether defects and the defect size exert effects on crystallization, melting behaviors, and chain stacking of precision PEs.